Adeno-associated viral tools to trace neural development and connectivity across amphibians

Amphibians, by virtue of their phylogenetic position, provide invaluable insights on nervous system evolution, development, and remodeling. The genetic toolkit for amphibians, however, remains limited. Recombinant adeno-associated viral vectors (AAVs) are a powerful alternative to transgenesis for labeling and manipulating neurons. Although successful in mammals, AAVs have never been shown to transduce amphibian cells efficiently. We screened AAVs in three amphibian species—the frogs Xenopus laevis and Pelophylax bedriagae and the salamander Pleurodeles waltl—and identified at least two AAV serotypes per species that transduce neurons. In developing amphibians, AAVs labeled groups of neurons generated at the same time during development. In the mature brain, AAVrg retrogradely traced long-range projections. Our study introduces AAVs as a tool for amphibian research, establishes a generalizable workflow for AAV screening in new species, and expands opportunities for cross-species comparisons of nervous system development, function, and evolution. [Display omitted] •Scalable cross-species pipeline established for in vivo AAV serotype screening•AAVs transduce amphibian neurons across CNS regions and developmental stages•AAVs label isochronic cohorts of neurons in the developing amphibian CNS•AAVs facilitate retrograde tracing of amphibian neural circuits Jaeger et al. expand the toolkit for neuroscientists working on non-conventional animal species. The authors establish a screening strategy identifying adeno-associated viral vectors (AAVs) for three amphibian species and demonstrate that AAVs can deliver transgenes to the developing and mature CNS in both widespread and targeted manners.